681151993 has 2 divisors, whose sum is σ = 681151994. Its totient is φ = 681151992.

The previous prime is 681151987. The next prime is 681152053. The reversal of 681151993 is 399151186.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 359595369 + 321556624 = 18963^2 + 17932^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-681151993 is a prime.

It is not a weakly prime, because it can be changed into another prime (681151963) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 340575996 + 340575997.

It is an arithmetic number, because the mean of its divisors is an integer number (340575997).

Almost surely, 2^681151993 is an apocalyptic number.

It is an amenable number.

681151993 is a deficient number, since it is larger than the sum of its proper divisors (1).

681151993 is an equidigital number, since it uses as much as digits as its factorization.

681151993 is an evil number, because the sum of its binary digits is even.

The product of its digits is 58320, while the sum is 43.

The square root of 681151993 is about 26098.8887311318. Note that the first 3 decimals coincide. The cubic root of 681151993 is about 879.8622343737.

The spelling of 681151993 in words is "six hundred eighty-one million, one hundred fifty-one thousand, nine hundred ninety-three".